Liquid sensitive switch



' April ,1969 T. ca. VINCENT 3,437,769

LIQUID SENSITIVE SWITCH Filed'Marc h 15, 1967 INVENTOR. THOMAS G. VINCENT "MW/ M1 ATTORNEY United States Patent US. Cl. ZOO-61.04 5 Claims ABSTRACT or THE DISCLOSURE Ions are produced by wetting an area between two bimetal strips which have been treated with sodium chloride. The ions support a current flow when a potential is impressed across the strips, the current heating the wetting agent and causing the bimetal strips to bend, contact, and complete a primary circuit.

Background of the invention The invention pertains generally to liquid sensing switches and particularly to a liquid sensing switch which responds to the heat produced by an electrical current which flows through the liquid when it is present.

Brief description of the drawings FIGURE 1 is an orthographic representation of one embodiment of the switch; and

FIGURE 2 is an orthographic representation of a second embodiment of the switch.

Description of the preferred embodiments In FIGURE 1 a pair of bimetal strips and 12 are firmly held at one end in a sleeve 14 containing a potting material 16. Any other holding arrangement may be provided which rigidly supports and provides electrical insulation between strips 10 and 12. Mounted on the other ends of strips 10 and 12 are contacts 18 and 20 respectively. A source of energy 22 and a load means 24 are connected in series with the ends of the strips embedded in sleeve 14. Areas 26 and 28 on strips 10 and 12 respectively are treated with a salt material, e.g., sodium chloride. In general the material applied at areas 26 and 28 should be soluble in the liquid being sensed. In this way ions are produced. If the liquid being sensed is relatively conductive a salt material is not necessary.

The bimetal strips do not have to be treated with an ion producing salt if the wetting agent already contains ions or if the wetting agent has been directed over a salt prior to entry between the strips.

Bimetal compensation may be used in the apparatus of FIGURE 1. The bimetal strips 10 and 12 may be made of different materials whereby one strip will bend faster than the other and the slower one can bend in either the opposite or the same direction. This would allow delayed or controlled closing action within a single basic design.

In FIGURE 2 a second embodiment is shown which is similar to that in FIGURE 1. The switch shown in FIGURE 2 differs from that shown in FIGURE 1 in that strip 12 is not a bimetal strip as is strip 12 in FIGURE 1. The position or shape of strip 12 is fixed whereas strip 12 in FIGURE 1 is bent or deformed in accordance with the heat produced between the areas 26 and 28.

The switch in FIGURE 1 operates when water or a 3,437,769 Patented Apr. 8, 1969 similar liquid is present between strips 10 and 12 in the areas 26 and 28. Ions are produced by the interaction of the liquid and the salt materials deposited on areas 26 and 28 and a relatively small current is set up between strips 10 and 12 in these areas. The production of ions between strips 10 and 12 in the areas 26 and 28, respectively, eifectively closes a series circuit comprising energy source 22 and load means 24. This current generates heat between the wetted areas 26 and 28 causing the water or similar liquid present to heat. The heat generated in this process causes strips 10 and 12 to bend together closing contacts 18 and 20. When contacts 18 and 20 close a relatively heavy current flows in the series circuit comprising the strips 10 and 12, energy source 22 and load 24. It is to be noted that in the first stage of operation a relatively small current exists whereas in the second stage of operation a relatively heavy current exists. The heavy current will exist until strips 10 and 12 cool and bend apart. During this time a control function can be carried out by the load means. Closing contacts 18 and 20 shorts or shunts the current path between areas 26 and 28 but strips 10 and 12 hold in long enough to perform some predetermined control function.

The switch embodiment shown in FIGURE 2 operates substantially in the same manner as that shown in FIG URE 1. The only difference being that strip 12' does not bend. Strip 10 in FIGURE 2 is identical to strip 10 in FIGURE 1 and it operates in FIGURE 2 to bend and thereby cause contact 18 on strip 10 to make with contact 20 on strip 12'.

A resistor-capacitor combination (not shown) may be placed in parallel with contacts 18 and 20 to prevent arcing when they make and break. The material used to treat areas 26 and 28 depends upon the liquid which is being sensed. For example, if the liquid is rain water, the material can be a water soluble salt such as sodium chloride. Naturally other liquid-material combinations may be used. In fact, special treatment of areas 26 and 28 may not be necessary depending upon the fluid or liquid which is being detected. If the liquid is relatively conductive, then special treatment of areas 26 and 28 may not be necessary. It should also be obvious that the strips 10 and 12 need not be bimetallic along their entire length.

I claim:

1. A liquid sensing system, comprising:

a pair of strips, at least one of which moves in response to heat;

an electrical energy source; and,

a load device, the source and load connected in series circuit with the strips, any liquid situated between the strips completing the series circuit, causing current to flow, heating the liquid, and the heat from the liquid causing at least one strip to bend and contact the other.

2. The system of claim 1 wherein at least one of the strips is at least partly bimetallic.

3. The system of claim 1 wherein at least one of the strips is treated with a material which is soluble in the liquid and produces ions.

4. A switch for use in a liquid sensing control system, comprising:

a pair of bimetallic strips, an area on at least one of them coated with a material soluble in the liquid; and,

3 4 a sleeve-like insulating element generally surrounding References Cited one pair of corresponding ends of said strips, holding UNITED STATES PATENTS the strips in a coextensive, spaced-apart, generally 1969 955 8/1934 Thomas parallel arrangement, the other pair of ends free to 2:284:103 5/1942 Smithy move and meet- 5 3,200,388 8/1965 Uhlig ZOO-61.04

5. The apparatus of claim 4 wherein the liquid is D water and the material soluble in the water is sodium ROBERT SCHAEFER Pnmary chloride. H. O. JONES, Assistant Examiner. 

